The present invention relates to tube cutting apparatus for use in a continuous tube manufacturing die set and, more particularly, to tube cutting apparatus of the double cut type including a tube notching blade and a tube severing blade. The apparatus includes quick change features for accommodating replacement and/or installation of the tube severing blade and the tube engaging die jaws and an arrangement for ensuring the proper positioning of the horizontal notching surface of the notching blade relative to the die jaws.
In tube cutting apparatus of the double cut type, as the term is commonly referred to in the art, tubing is continuously passed through a tube cutoff die set wherein a notching cut in the tubing wall is followed by a vertical tube severing cut. Exemplary of such apparatus are Riera et al. "Tube Cutoff Die Set" U.S. Pat. No. 4,653,368 and "Replaceable Die Sets" U.S. patent application Ser. No. 222,947, filed July 22, 1988, the disclosure of each being specifically incorporated herein by reference.
Generally, the tube cutting apparatus includes means for moving tubing along a generally horizontal feed path, means for performing a notching cut by a notching blade mounted for reciprocal movement horizontally across the tube path, an axially elongated cutoff blade mounted for vertical severing movement following the notching cut, and tube holding means for releasably clamping the tube on both sides of the severing plane. Because continuous operation of the machine is important, downtime lost to changing tube clamping die jaws to accommodate different tube diameters should be held to a minimum. Further, downtime due to breakage of the tube severing blade or the need to change the blade to utilize a different cutting edge should also be held to a minimum for the same reason.
Accordingly, an object of the present invention is provision of a quick change arrangement whereby the tube severing blade and tube engaging jaw holders may be rapidly changed to effect different tube diameters.
Further, in a preferred form, the notching and tube severing blades both pass through a vertical passage defined between complemental pairs of die jaws. When the severing blade is in its upward vertical position the notching blade is in its rest position but hidden from view in the vertical passage between adjacent die jaws. To avoid dimples in the severed tube, the depth of the notching cut is of extreme importance. However, the exact location of the notching surface and thus the horizontal path of the notching blade is not truly known until the ram assembly has moved downwardly.
Accordingly, another object of this invention is provision of a quick and accurate arrangement and method for checking and adjusting, when needed, the position of the notching blade path relative to the die jaws.
When severing larger diameter tubes, the passage width may need to be changed as well as the notching and severing blades. To increase the width of the passage the user will oftentimes stuff a shim downwardly between the jaw and jaw holder. Use of shims can place bending moments on the jaws leading to their possible destruction. Further, these shims have typically not been precision parts but have comprised paper-thin metal sheets. In the past, blade holding blocks have been found to wear adversely and then require the user to replace an expensive machine part.
Accordingly another object of this invention is provision of an arrangement, useful in conjunction with the jaw holders and blade holder, which assures the user that the severing blade is properly disposed in its vertical severing plane.
In accordance with the present invention there is provided to each respective die jaw an arrangement which quickly allows the user to remove the die jaw from its jaw holder. Further, a clamping arrangement allows the tube severing blade to be rapidly installed and/or removed with its center axis aligned so as to not be angularly offset relative to a perpendicular vertically through the tube axis and lower die shoe. Exchanging the jaws or the severing blade is accomplished with a minimum of downtime and thus is relatively inexpensive.
To ensure the proper depth of the tube notch, the notching blade and the die jaws have gauging surfaces positioned relative to one another and preferably to the die shoe. In this regard, the notching blade has a first gauging surface vertically spaced by a preset amount from the notching surface and the top surface of the die jaw defines a second gauging surface spaced by a preset amount from the tube and the die shoe, the notching, gauging and die shoe surfaces being in a respective horizontal plane. Advantageously, maintaining the vertical spacing between the notching and gauging surfaces of the notching blade allows the user during sharpening of the notching blade to accurately set the horizontal plane of the notching surface for any given tube diameter and tube thickness.
In use, the user positions a precision gauging block on the gauging surface of the die jaw and then lowers the notching blade to bring its gauging surface against the block, thereby positioning the notching surface of the blade. In one aspect, a single replaceable cartridge carrying the die shoes could be removed from the press and gauging could be achieved by placing a reference gauge between the die shoe and either of the notching and gauging surfaces of the notching blade.
Other advantages and features will become apparent from the following specification taken in connection with the accompanying drawings.